Ablation system with catheter clearing abrasive

ABSTRACT

An ablation system is provided that comprises an atherectomy device and an aspiration catheter, each routed to a position just proximal to a lesion within a patient&#39;s vessel to ablate and remove the lesion so that blood flow through the vessel is adequately restored. The atherectomy device includes a flexible driveshaft coupled to an ablation burr. The ablation burr includes a concave front surface having an abrasive disposed thereon and a generally frusto-conical rear surface having an abrasive disposed thereon. The aspiration catheter has an elongate body and includes a centrally located lumen that is separated into two portions having different inner geometries. The two portions consist of a generally constant inner diameter portion and a frusto-conical distal portion. The distal portion of the lumen is positioned approximately at the distal end of the catheter to define an aspiration mouth. The distal portion narrows from the distal end of the catheter toward the proximal end of the catheter in an inwardly tapered manner to form generally frusto-conical inner surface. The taper of the inner surface of the catheter generally corresponds to the taper of the rear surface of the ablation burr so that the ablation burr may be pulled back into the distal portion of the lumen of the catheter during operation of the system.

FIELD OF THE INVENTION

[0001] The present invention generally relates to devices for removingundesirable deposits from the lumen of a blood vessel or from a stentpositioned within a blood vessel, and more particularly, to atherectomydevices.

BACKGROUND OF THE INVENTION

[0002] Vascular diseases, such as atherosclerosis and the like, havebecome quite prevalent in the modern day. These diseases may presentthemselves in a number of forms. Each form of vascular disease mayrequire a different method of treatment to reduce or cure the harmfuleffects of the disease. Vascular diseases, for example, may take theform of deposits or growths in a patient's vasculature which mayrestrict, in the case of a partial occlusion, or stop, in the case of atotal occlusion, blood flow to a certain portion of the patient's body.This can be particularly serious if, for example, such an occlusionoccurs in a portion of the vasculature that supplies vital organs withblood or other necessary fluids.

[0003] To treat these diseases, a number of different therapies arebeing developed. While a number of invasive therapies are available, itis desirable to develop noninvasive therapies as well. Non-invasivetherapies may be less risky than invasive ones, and may be more welcomedby the patient because of the possibility of decreased chances ofinfection, reduced post-operative pain, and less post-operativerehabilitation. One type of non-invasive therapy for vascular diseasesis pharmaceutical in nature. Clot-busting drugs have been employed tohelp break up blood clots, which may be blocking a particular vascularlumen. Other drug therapies are also available. Further non-invasive,intravascular treatments exist that are not only pharmaceutical, butalso revascularize blood vessels or lumens by mechanical means. Twoexamples of such intravascular therapies are balloon angioplasty andatherectomy that physically revascularize a portion of a patient'svasculature.

[0004] Balloon angioplasty comprises a procedure wherein a ballooncatheter is inserted intravascularly into a patient through a relativelysmall puncture, which may be located proximate the groin, andintravascularly navigated by a treating physician to the occludedvascular site. The balloon catheter includes a balloon or dilatingmember that is placed adjacent the vascular occlusion and then isinflated. Intravascular inflation of the dilating member by sufficientpressures, on the order of 5 to 12 atmospheres or so, causes the balloonto displace the occluding matter to revascularize the occluded lumen andthereby restore substantially normal blood flow through therevascularized portion of the vasculature. It is to be noted, however,that this procedure does not remove the occluding matter from thepatient's vasculature, but displaces and reforms it.

[0005] While balloon angioplasty is quite successful in substantiallyrevascularizing many vascular lumens by reforming the occludingmaterial, other occlusions may be difficult to treat with angioplasty.Specifically, some intravascular occlusions may be composed of anirregular, loose or heavily calcified material which may extendrelatively far along a vessel or may extend adjacent a side branchingvessel, and thus are not prone or susceptible to angioplastic treatment.Even if angioplasty is successful, thereby revascularizing the vesseland substantially restoring normal blood flow therethrough, there is achance that the occlusion may recur. Recurrence of an occlusion mayrequire repeated or alternative treatments given at the sameintravascular site.

[0006] A relatively new technique to reduce the recurrence of occlusionafter a balloon angioplasty procedure involves providing a stent at therevascularized site. A stent is a hollow tube, typically braided, thatcan be inserted into the vasculature of a patient in a compressed form.Once properly positioned at a desired site, the stent is expanded tohold the vessel open in an attempt to prevent restenosis. While thistechnique can help maintain blood flow past the site, it has been foundthat the occluding material often migrates through the interstices ofthe stent braid, and may again occlude the vessel. This phenomenon issometimes referred to as interstitial hyperplasia.

[0007] Accordingly, attempts have been made to develop other alternativemechanical methods of non-invasive, intravascular treatment in an effortto provide another way of revascularizing an occluded vessel and ofrestoring blood flow through the relevant vasculature. These alternativetreatments may have particular utility with certain vascular occlusions,or may provide added benefits to a patient when combined with balloonangioplasty and/or drug therapies.

[0008] One such alternative mechanical treatment method involvesremoval, not displacement, as is the case with balloon angioplasty, ofthe material occluding a vascular lumen. Such treatment devices,sometimes referred to as atherectomy devices, use a variety of means,such as rotating cutters or ablaters, for example, to remove theoccluding material. The rotating cutters may be particularly useful inremoving certain vascular occlusions.

[0009] In operation, an atherectomy device is typically advanced over aguide wire placed in vivo until the device is positioned just proximalto the occluded site. A motor is used to rotate a driveshaft coupled tothe device, and the device is moved through the occluded vessel.Frequently, an aspiration device is utilized in conjunction with thedevice to remove the loose particulate broken off by the device so thatthe particulate is not introduced into the body. Typically, aconventional aspiration device consists of a catheter in fluidcommunication with a vacuum source or negative pressure such as a vacuumpump or bottle. The catheter, generally surrounding the driveshaft, isadvanced to the occlusion site over the guide wire to remove the looseparticulate.

[0010] However, problems can occur when treating various vessels of thepatient. For example, in saphenous vein grafts (SVG) and with stentedvessels, the occluding material or gromous has a tendency to be moreloosely organized and brittle, which makes the material friable.Therefore, in operation, conventional devices tend to break off largepieces of this material rather easily due to its morphology, instead ofablating it. These large particulate are then sucked into the mouth ofthe aspirating catheter, causing the loose particulate to become lodgedin the mouth of the catheter. As a result, the occlusion site ispresented with a lack of vacuum pressure that could hinder theaspiration process.

[0011] Therefore, there exists a need for an improved ablation burrsystem and process for removal of large, liberated particulate within anoccluded blood vessel to overcome the deficiencies in the prior art.

SUMMARY OF THE INVENTION

[0012] An ablation system is provided to overcome the deficiencies inthe prior art. The ablation system comprises an atherectomy device andan aspiration catheter, each routed to a position just proximal to alesion within a patient's vessel to ablate and remove the lesion so thatblood flow through the vessel is adequately restored.

[0013] In one embodiment of the invention, an ablation system includes adriveshaft, an ablation burr coupled to the driveshaft and an aspirationcatheter. The aspiration catheter has a trap for collecting particles ofoccluding matter that are ablated by the burr.

[0014] In accordance with another aspect of the present invention, amechanism is provided that cooperates with the trap on the aspirationcatheter to clear collected particles from the trap.

[0015] In accordance with yet another aspect of the present invention, asystem for ablating an occlusion in a patient's vessel comprises anablation burr having a front surface and a rear surface, and beingrotatable to ablate the occlusion. The system also comprises anaspiration catheter having proximal and distal ends. The catheterincludes a lumen that extends longitudinally therethrough. The lumenforms an aspiration mouth at the distal end of the aspiration catheter,where the aspiration catheter includes a tapered inner surface defininga portion of the lumen.

[0016] In accordance with still another aspect of the present invention,a method is provided for ablating a lesion in a patient's vessel usingan ablation burr system. An atherectomy burr is routed to a positionjust proximal to the lesion, the burr having a downwardly tapering rearsurface. An aspiration catheter is routed to a position just proximal tothe burr, the aspiration catheter having proximal and distal ends andincluding a lumen that extends longitudinally therethrough. The lumenforms an aspiration mouth at the distal end of the aspiration catheter,where the aspiration catheter includes a tapered inner surface defininga portion of the lumen. The burr is advanced distally through the lesioncausing loose particulate to separate from the vessel wall. The looseparticulate is aspirated with the aspiration catheter. The aspirationmouth of the aspiration catheter is cleared by pulling the burrproximally toward the aspiration catheter so that the burr can breakdown the loose particulate for removal by the catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The foregoing aspects and many of the attendant advantages ofthis invention will become more readily appreciated as the same becomebetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

[0018]FIG. 1 is a side elevation view of an exemplary embodiment of anablation burr system within an occluded vessel in accordance withaspects of the present invention;

[0019]FIG. 2 is a partial cross-sectional view of an exemplaryembodiment of an atherectomy device shown in FIG. 1;

[0020]FIG. 3 is a partial cross-section view of an exemplary embodimentof an aspiration catheter shown in FIG. 1;

[0021]FIG. 4 is a cross-sectional view of the exemplary embodiment ofthe ablation burr system shown in FIG. 1 wherein the atherectomy deviceis advanced away from the aspiration catheter;

[0022]FIG. 5 is a cross-section view of an exemplary embodiment of theablation burr system shown in FIG. 1 wherein the atherectomy device ispulled proximally toward and within the aspiration catheter;

[0023]FIG. 6 is a perspective view of an exemplary embodiment of thedistal end portion of the aspiration catheter shown in FIG. 1;

[0024]FIG. 7 is an end view of an alternative embodiment of theaspiration catheter in accordance with aspects of the present invention;

[0025]FIG. 8 is a perspective view of a distal end portion of analternative embodiment of the aspiration catheter illustrating acontoured inner tapered portion; and

[0026]FIG. 9 is an end view of an alternative embodiment of theaspiration catheter illustrating a different cross-sectional geometry ofthe aspiration mouth.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0027]FIG. 1 illustrates an exemplary embodiment of an ablation burrsystem 20 within an occluded vessel V, such as an SVG, having a lesion Lin it. The ablation system 20 comprises an atherectomy device 22 and anaspiration catheter 24, each routed to a position just proximal to thelesion L to ablate and remove the lesion L so that the blood flowthrough the vessel V is adequately restored.

[0028] Referring now to FIG. 2, the atherectomy device 22 includes aflexible driveshaft 26 coupled to an ablation burr 28. The flexibledriveshaft 26 has a lumen 30 extending therethrough to receive a guidewire 34, as shown. The driveshaft 26 is coupled at its proximal end to asource of rotational motion such as an electric motor or gas turbine(not shown) that rotates the driveshaft at high speeds, e.g., between20,000 and 250,000 rpm. In operation, with reference to FIGS. 1 and 2,the guide wire 34 is percutaneously inserted through the vasculature ofa patient, and past the site of the lesion L. The atherectomy device 22is then routed to a point near the site of lesion L over the guide wire34 by an advancer, not shown but well known in the art. A guide catheter36, shown in FIGS. 4 and 5, may be used to assist in the positioning ofboth the guide wire 34 and the atherectomy device 22, also known in theart. Extending through the guide catheter 36 is the aspiration catheteror sheath 24 for aspirating loose particulate 40 that breaks off duringablation. The ablation burr 28, when rotated by the driveshaft 26,ablates a new lumen through the lesion L in order to permit blood toflow freely through the vessel V. The aspiration catheter 24, due to thepresence of a vacuum or negative pressure, removes the loose particulate40 from within the vessel.

[0029] Referring to the exemplary embodiment of the present inventionshown in FIG. 2, the atherectomy device 22 of the ablation system 20preferably comprises a flexible driveshaft 26 coupled to an ablationburr 28, wherein the flexible driveshaft 26 and the ablation burr 28 aredisposed about a central axis. The ablation burr 28 is preferablyconstructed from a metallic material such as brass, and is shaped tohave a generally concave front or leading surface 42 and a generallyfrusto-conical rear or trailing surface 44. In the embodiment shown, theconcave front surface 42 extends from an inner circumferential rim oredge portion 46 at the distal tip of the burr 28 to a ridge or crest 48disposed approximately at the midpoint of the burr 28. Thefrusto-conical rear surface 44 extends from an inner circumferential rimor edge portion 50 at the proximal tip of the burr 28 to the ridge 48.Accordingly, the ridge 48 has an outer diameter greater than eitherinner circumferential edge portions 46, 50.

[0030] As shown in FIG. 2, an axial socket 52 is disposed along thecentral axis and extends through the frusto-conical rear surface regionof the burr 28 for receiving the end of the driveshaft 26. The ablationburr 28 further includes a guide wire lumen 54 concentric with buthaving a smaller diameter than the axial socket 52. The guide wire lumen54 extends from the distal end of the axial socket 52, through theconcave front surface 42, and terminates at the distal end of theablation burr 28 so that the ablation burr 28 may be threaded over guidewire 34.

[0031] As indicated above, the front surface 42 of the burr is concavein cross section and is partially or totally covered with an abrasivematerial 58 such as diamond grit to ablate the lesion L when the burr isrotated. The frusto-conical shaped rear surface 44 of the burr is alsototally or partially covered with an abrasive material 60 such asdiamond grit, the purpose of which is discussed in more detail below.The abrasive material 58, 60, can be secured on the outer surfaces 42,44, of the burr by any conventional method such as electro and/orelectroless plating. A smooth or non-abrasive portion 62 of the burrhaving a non-abrasive surface is preferably formed between the abrasivematerial 58, 60, found at the distal end and proximal ends of the burr.The non-abrasive portion 62 preferably begins at a point of maximumdiameter of the burr and continues proximally along a portion of therear surface 44 of the burr in order to reduce irritation at the vesselwalls.

[0032] Referring now to FIG. 3, the aspiration catheter 24 is routed toa position just proximal to the site of the lesion adjacent to theablation burr so that the catheter 24 can aspirate or remove the looseparticulate that might be broken off by the ablation burr. Theaspiration catheter 24 is in fluid communication with a vacuum source(not shown) such as a vacuum pump or bottle as is know in the art. Itwill be appreciated that other devices (not shown) may be used inconjunction with vacuum source such as a blood filter and pump to returnthe aspirated blood to the patient. The aspiration catheter 24 has anelongate body of a generally cylindrical shape and includes a centrallylocated lumen 80 so that the driveshaft 26 can extend therethrough. Thelumen 80 also provides an conduit for loose particulate to be removedfrom the vessel.

[0033] As shown in FIGS. 3 and 6, the centrally located lumen 80 isconcentric with the driveshaft 26 and is separated into two portionshaving different inner geometries. The two portions consist of agenerally constant inner diameter proximal portion 82 and a generallyconical distal portion 84. The distal portion 84 of the lumen 80 ispositioned approximately at the distal end of the catheter 24 anddefines an aspiration mouth 86 for receiving the loose particulate asvacuum or negative pressure is supplied to the catheter 24 via thecentrally located lumen 80. The distal portion 84 narrows from thedistal end of the catheter 24 toward the proximal end of the catheter 24in an inwardly tapered manner to form a generally conical inner surface90. The taper of the inner surface 90 of the catheter 24 generallycorresponds to the taper of the rear surface 44 of the ablation burr 28,as best shown in FIGS. 4 and 5, so that the ablation burr may be pulledback into the distal portion 84 of the lumen 80 during operation of theablation burr system 20.

[0034] In the embodiment shown, the diameter of the aspiration mouth 86is substantially equal to the diameter formed by the generally constantinner diameter proximal portion 82. The constant inner diameter portion82 extends from the proximal end of the aspiration catheter 24 towardthe distal end of the aspiration catheter 24. A small, generallycylindrical lumen 88 having a substantially constant diameter mayconnect the proximal and distal portions 82, 84 to provide an integrallumen 80 extending through the catheter 24.

[0035] The inner surface 90 of the aspiration catheter 24 may besuitably contoured or textured to help grab or retain the looseparticulate within the catheter 24. For example, a plurality of elongateribs or splines 92 may be positioned around the inner surface 90 of theaspiration catheter 24 to hold the loose particulate, as shown in FIGS.7 and 8. Alternatively, the aspiration mouth 86 may have a differentcross-sectional geometry, such as a star-shaped opening shown in FIG. 9which can act as a filter to collect the loose particulate at or nearthe mouth 86 of the aspiration catheter 24. While the embodiments shownare exemplary of suggested configurations, it will be readily apparentto those skilled in the art that any one of a variety of suitable innersurface textures or aspiration mouth geometric openings are within thescope of the present invention.

[0036] The operation of the ablation system constructed in accordancewith aspects of the present invention will now be described withreference to FIGS. 1, 4 and 5. The ablation burr 28 is routed over theguide wire 34 to the site of the lesion L. The aspiration catheter 24 isthen routed to just proximal the ablation burr 28. The ablation burr 28is spun up to speed by the driveshaft 26, which is rotated by rotationalmeans such as a gas turbine or an electric motor. As the burr 28 isrotated, the burr 28 is advanced through the lesion L by the advancer(not shown), whereby the abrasive 58 positioned on the front surface 42of the burr 28 ablates the lesion L. During the ablation procedure,loose particulate 40 that was not completely ablated is detached fromthe vessel wall and remains suspended within the blood of the vessel V.A slight vacuum present at the mouth 86 of the aspiration catheter 24pulls the loose particulate 40 within the mouth 86 of the catheter 24.Due to the presence of the frusto-conical inner surface 90 within themouth 86 of the catheter 24, large pieces of the loose particulate 40are trapped between the driveshaft 26 and the frusto-conical innersurface 90 of the aspiration catheter 24.

[0037] After the lesion L is fully ablated or when the physician noticesa drop in aspiration pressure, the ablation burr 28 may be pulled backby the advancer toward the mouth 86 of the aspiration catheter 24. Dueto the tapered rear surface 44 of the ablation burr 28, the ablationburr 28 may be pulled into the mouth 86 of the aspiration catheter 24.The ablation burr 28, still rotating via the driveshaft 26, ablates orbreaks up the loose particulate 40 trapped within the aspirationcatheter 24 due to the abrasive material 60 disposed on the rear surface44 of the ablation burr 28. The loose particulate 40 is broken up intosuitable dimensioned pieces 94 by the ablation burr 28 so that it may beremoved by the aspiration catheter 24.

[0038] While the preferred embodiment of the invention has beenillustrated and described, it will be appreciated that various changescan be made therein without departing from the scope of the invention.For example, the aspiration catheter need not have afrusto-conically-shaped lumen at its distal end. Other shapes that bothtrap ablated particles between the lumen walls and the driveshaft aswell as cooperate with the rear of the burr to clear the catheter couldbe used. Such shapes could be cylindrical, ovoidal, etc. Similarly, therear surface of the ablation burr could include a number of blades thatfit within the distal end of the aspiration catheter to clear trappedparticles. If the catheter has a star-shaped or slotted lumen, as shownin FIGS. 7-9, then the rear surface of the burr may have a correspondingshape to clear the entrance to the catheter. Such shapes may be like akey such that they fit within the catheter when the burr is notrotating. It is therefore intended that the scope of the invention bedetermined from the following claims and equivalents thereof.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An aspiration catheterfor use in an ablation system comprising: an elongate body havingproximal and distal ends; a lumen extending longitudinally within saidbody and terminating at an aspiration mouth at said distal end of saidbody; wherein said lumen has a tapered inner surface at a positionproximal to said aspiration mouth.
 2. The catheter of claim 1, whereinsaid tapered inner surface tapers from a first diameter at saidaspiration mouth to a second, smaller diameter positioned proximal tosaid aspiration mouth.
 3. The catheter of claim 2, wherein said lumenfurther includes a third substantially constant inner diameter portionthat extends proximally from said second diameter.
 4. The catheter ofclaim 3, wherein said lumen has a fourth diameter portion that extendsproximally of the third diameter portion, said fourth diameter portionhaving a diameter substantially equal to said first diameter.
 5. Thecatheter of claim 1, wherein said aspiration catheter includeslongitudinally extending splines disposed around said tapered innersurface.
 6. The catheter of claim 1, wherein said aspiration mouth beingoperative as a filter.
 7. The catheter of claim 1, wherein saidaspiration mouth forms a star shaped opening, said opening beingoperative as a filter.
 8. A system for ablating a lesion in a patient'svessel comprising: a driveshaft; an ablation burr coupled to saiddriveshaft, said ablation burr having a distal end and a proximal end;and an aspiration catheter including a longitudinally extending lumenhaving an aspiration mouth at the distal end of the aspiration catheter;wherein said aspiration catheter includes a frusto-conically shapedlumen adjacent the aspiration mouth.
 9. The system of claim 8, whereinsaid ablation burr includes front portion and a frusto-conically shapedrear portion that fits within the frusto-conically shaped lumen of theaspiration catheter.
 10. The system of claim 9, wherein said rearportion of said burr has an abrasive surface.
 11. The system of claim 9,wherein said ablation bur includes a nonabrasive portion, saidnon-abrasive portion positioned between said front portion and saidfrusto-conically shaped rear portion.
 12. The catheter of claim 8,wherein said aspiration catheter includes one or more longitudinallyextending splines disposed around said frusto-conically shaped lumen.13. The catheter of claim 8, wherein said aspiration mouth is operativeas a filter.
 14. The catheter of claim 8, wherein said aspiration mouthforms a star shaped opening, said opening being operative as a filter.15. A system for ablating an occlusion in a patient's vessel comprising:an ablation burr having a front surface and a rear surface, said burrbeing rotatable to ablate the occlusion; and an aspiration catheterhaving proximal and distal ends, said catheter including a lumenextending longitudinally therethrough, said lumen forming an aspirationmouth at said distal end of said aspiration catheter; wherein saidaspiration catheter includes a tapered inner surface defining a portionof said lumen.
 16. The system of claim 15, wherein said front and rearsurfaces include an abrasive disposed thereon.
 17. The system of claim16, wherein said rear surface of said burr tapers downwardly to thedistal end of said burr.
 18. The system of claim 17, wherein the slopeof said tapering rear surface of said burr corresponds to the slope ofsaid tapered inner surface of said aspiration catheter.
 19. The systemof claim 15, wherein said aspiration mouth opens adjacent to said rearsurface of said ablation burr.
 20. The system of claim 15, wherein saidaspiration catheter includes longitudinally extending splines disposedaround said tapered inner surface.
 21. The system of claim 15, whereinsaid aspiration mouth being operative as a filter.
 22. A method forablating a lesion in a patient's vessel using an ablation burr systemcomprising: routing an atherectomy burr on a driveshaft to a positionjust proximal to said lesion, said burr having a downwardly taperingrear surface; routing an aspiration catheter over the driveshaft to aposition just proximal to said burr, said aspiration catheter havingproximal and distal ends and including a lumen extending longitudinallytherethrough, said lumen forming an aspiration mouth at said distal endof said aspiration catheter, wherein said aspiration catheter includes acontoured inner surface that mates with a rear surface of the ablationburr; rotating and advancing said burr distally through said lesioncausing loose particulate to separate from the vessel wall; aspiratingsaid loose particulate with said aspiration catheter; clearing saidaspiration mouth of said aspiration catheter by pulling said burrproximally toward said aspiration catheter so that said rear surface ofthe burr is urged toward the contoured surface of the lumen to breakdown said loose particulate for removal by said catheter.
 23. The methodof claim 22, wherein said clearing said aspiration mouth of saidaspiration catheter occurs during the ablation process when a loss inaspiration pressure is determined.
 24. The method of claim 22, whereinsaid clearing said aspiration of said aspiration catheter occurs afterthe lesion has been fully ablated and the blood flow has been restored.25. An aspiration catheter for use with an ablation system of the typethat includes an ablation burr rotated by a driveshaft, the catheterhaving a lumen that extends along its length, wherein the lumen includesa tapered portion having a diameter that is wider at its distal end andnarrows such that larger pieces of particulate removed by the ablationburr become trapped in the tapered portion of the lumen, the taperedportion further being shaped to receive a rear surface of the burr toclear the catheter of the trapped particulate.
 26. A system for removingmatter from a patient's vessel, comprising: a driveshaft; an ablationburr coupled to the driveshaft for removing matter from a patient'svessel; an aspiration catheter through which the driveshaft is routed,the aspiration catheter including means for trapping ablated particlesnear the distal end of the aspiration catheter; and means for clearingthe trapped particles from the distal end of the catheter.
 27. A systemfor removing occluding matter from a patient's vessel, comprising: adriveshaft; an ablation burr coupled to the driveshaft, the burr havinga leading abrasive surface for removing occluding matter from the vesselwhen rotated by the driveshaft and an abrasive rear surface; anaspiration catheter through which the driveshaft is routed, including atrap for capturing ablated material near the distal end of theaspiration catheter, the trap being configured to cooperate with theabrasive rear surface of the burr to clear captured ablated materialfrom the aspiration catheter.